Photographic process for reproducing multicolor images



May 16, 195% MULTICOLOR IMAGES 3 Sheets-Sheet 1 Filed Feb. 21, 1950 5 O 5. 0 wmzommmm m mm mmzomwmm mZC mm .m M m A V H m P E s 0 m v M MA w c .w n o G .W .m o O R .l H T G N E L E G M A MA 0 w 0 \OJ 4 4 \L 0 I. G CI {7W gamma ATTORNEY y 16, 1959 .1. A. BALL 2,508,213

PHOTOGRAPHIC PROCESS FOR REPRODUCING MULTICOLOR IMAGES Filed Feb. 21,. 1950 3 Sheets-Sheet 2 CHLOR RELATIVE RESPONSE INVENTOR.

SIOSEPHA. BALL WAVE LENGTH $Mllllmicrons) ATTORNEY May 16,1950

MULTICOLOR IMAGES Filed Feb. 21, 1950 3 Sheets-Sheet I5 VIOLET, BLUE, GREEN: CHLORX RED VIOLET: BLUE X GREEN: CHLOR RED 7 Lo 4(0 so sa e 'npo WAVE LENGTH (Millimicrons) INVENTOR.

JOSEPH A. BALL A TTORNEY Patented May 16, 1950 UNITED STATES PATENT OFFICE PHOTOGRAPHIC PROCESS FOR REPRODUC- ING MULTICOLOR IMAGES Joseph A. Ball, Los Angeles, Calif.

Application February 21, 1950, Serial No. 145,382

8 Claims. (01. 95-2) .1 This invention relates to processes for reproducing multicolor images utilizing five subtractive color components. In one of its useful aspects the invention relates to photographic processes for reproducing multicolor images which utilize five subtractive color components. Another useful aspect is concerned with processes for reproducing multicolor images utilizing five different colored substances.

This application is a continuation-in-part of copending application Ser. No. 771,790, filed September 2, 1947. i a

. An object of this invention is to provide new and improved methods of multicolor reproduction. Another object is to provide such processes which are superior to the prior art processes. Still further objects are to provide such processes wherein negative components are rendered ineffective todisturb the final subtractive picture. Still furtherobjects are. to provide such processes wherein five color components are used. Yet another object is to provide color reproduction processes whose color gamuts .will fill the spectrum locus on a uniform chromaticity diagram in such fashion as to enable the process to reproduce all colors with fidelity. Still other objects will be apparent from the following more detailed description of the invention and the accompanying drawings which constitute a part of the present specification.

My application U. S. Serial No. 771,790 describes the manner in which four spectral bands, or four sharp-cutting spectral absorbers, can be controlled in conformity with the fundamental trichromatic color mixture data, thereby producing a -primary process of color reproduction. In this application the method is extended to the control of five spectral bands or absorbers resulting in a E-primary process. In the application, Serial No. 771,790, the existence of five unique spectral bands is pointed out. Three of these bands, namely, violet, green and red are located well into the cornersof-the spectrum locus and the other two, blue and yellow.(chlor), represent the mid-sectionsof the two arms-of the spectrum locus. That application also points out that in practical processes there are as many as five conditions to bemet, namely, thethree conditions imposed by the three dimensional aspect of color space and additional ones by the requirements that the entire spectrum range be covered and that negative components of response be minimized. That application further points out that Iii-primary processes all demand a considerable' degree of compromise'so that improvement can be effected by passing to 4- or even 5-primary processes; but that application covers only the 4- primary process. p

In designing a 3-primary process the spectrum can be split in any desired manner, and three equal area responses deduced for the control of the three arbitrary bands, because there is only one way in which white light can be recreated, namely, by the addition of equal amounts of all three bands. However, in the case of 4- and 5- primary processes this is no longer true. In such processes there are a number of ways of balancing the primaries to recreate white light. The valuable ways for application to subtractive reproduction are those for which, in the additive version, equal parts of all of the 4 or 5 primaries are required to recreate white light, because only then can the subtractive version be viewed in ordinary white light. This in turn means that the response functions should all be of equal area. Therefore, in the substitution method described in the app. Ser. No. 771,790, wherein the yellow or chlor band is substituted for parts of the red and green bands, thereby producing a 4-primary process, it is of some importance that equal parts of the red and green bands should be simultaneously involved because only then can the equality of the response functions be maintained. This in turn means that there should be a complementarity between the blue-violet band and the chlor band. Now, complementarity usually implies a subjective judgment which varies with a specification of white. In a photographic reproduction process, the camera may view the original scene illuminated by one type of white light whilst the final result is viewed in an entirely different type of white light. In view of this lack of determination or specification of white it appears desirable to use the equal energy spectrum as a basis of computation; and it should be noted that complementarity in the equalenergy spectrum does have an objective significance. correspondingly, neutrality of a gray area (which likewise usually implies a subjective judgment) also has an objective meaning if it is defined as a uniform absorption of flux throughout the spectrum.

To proceed to the elaboration of the subject of this application, let us assume that the equal energy spectrum is divided into four bands, the cuts being at 505, 554 and 594. This is not a favorable arrangement for a 4-primary process, but, as will appear later, it is favorable for a 5- primary process. According to the revised I. C. I. distributions of Judd (J. O. S. A., November 1949) the chlor band, 554-594, is complementary to the blue-violet band, 380505, and matches in hue the sum of the red and green bands, but represents only 37% of the total intensity. If then we compute the three equal area responses for a 3-color process based upon the blue-violet, green and red bands (with the chlor band left out) we get the data plotted in Figure 1. The overlap of the red and green areas is 36% of the total area. If then instead of this 36% of combined red and green light we use a corresponding intensity of the chlor band, it appears that the triangular overlap area can serve as the response function for practically the entire chlor band. This leads to the four response functions shown in Fig. 2 which must be applied for the complete control of the 4 bands. The gamut which isprovided. by such a process is shown by the dashed line in Figure 3. (This figure is a Rectangular Uniform Chromaticity Scale of Breckenridge and Schaub (ref. J, O. S. A., vol. 29, 1 939 modified to be consistent with Judds data). As mentioned before, this is not a particularly favorable setup for a 4- color process because of the limitation of gamut in tlie blue-violet region and also because of the substantial negative components existing in both thered and green response functions at wavelengths shorter than 530.

It has been discovered that a decided improvement can readily be effected if we split the blueviolet-primary into its' component parts, blue and violet; and this will result in equal area responses if the split takes places at'o'r near the center of gravity or the blue-violet band, namely, 460. The essential data for these two bands usin Judds distribution-- functions are:

r dominant L Y Z z y hue By colorimetric. computations it is thenpossible to derive. equal area response functions for these two. separate bands; and: inthe; process the secondary positive and negative partsof the red and green response functionsain the blue and violet regions disappear. The combined results are shown in. Figure 4.. Simultaneously, the gamut of possible. reproduction colors has been enlarged to the pentagonal'figure shown in a solid line inzFigure 3.

The above describedresponses' have peaks and half-widths. as follows (all figuresv being given in: millimicrons):

Peak Half-"width Violet 430 45 Blue 482 45 Green 535 52 011101" 574 35 Rm 610 52 Bin imum allowable half-width is 60 millimicrons.

The essential features of the response functions such as specified here are all readily attainable in a photographic process by a proper choice of sensitizers and filters. More specifically, suitable separation negatives for a 5-primary process can be made by the combinations of Wratten filters and commercially available plates as listed below:

Record Wratten Filter Plate .Kodak Separation Negative Type 1.

SupeDr Ortho Press.

o. Kodak #33. 34- plus 2... Super Ortho Press.

24A plus 11 21 When it comes to a choice of pigments or colorants to provide a subtractive print in the S-primary process utilizing the novel response function's described above, additional. considerations must be given. Most practical colorants have broader absorption bands-than those speci' fled in the ideal: casedescribed above, that is to say, theyabsorb somewhat in bands other than those they are intended-to control. However, this is a common failing of subtractive colorants and. pigments even as used in a three primary process. The undesired absorptions can be countered by masking techniques- The: principles underlying the art of. masking. are well-- known and have been set forth ina number of articles and books. Seefor example, the article entitled Masking: a technique for improving: the quality of color reproductions, by T. H. Miller illJthel Journal of the Society of Motion Picture Engineers for February 1949,. or' a: series of articlesby- Preucil in the National. Lithographer during 1947 and'11948. selecting colorants-and applying masking procedures it makessome difference as to whether the subtractive method: isof the continuous tone type as in gravure: printing, or of the. half-tone dot type as in letterpress, or in lithographic printing.

Suitable colorants for a'half-tone. dot process are shown in Figure 5 and for a. continuous-tone process in Figure: 6.. In. Figure. a the precise colorants are:

Violet absorber. Hausa Yellow 130. Blue absorber P 'l M. A} precipitate of a basic Acridine Yellow of the fo1lowix1g-,.c'omp'ositiou:

40% of thelf: r: MIA. precipitate ofRhod'amine 66 (Q; L752); Glhlor. absorber--- Pltg zlotkm zgsltgc acidprecipitate of Rhodamine f 5 Rediab'sorbe'r Peacookl3lue' (Ref: Thel'che'mist'ry. and

absorber (which alone is a golden-yellow) pro-'- duces a deep yellow. Addition of the green absorber (which alone is pink) produces an orange- (and also to a lesser extent the red absorber) are contributing to the total absorption in the green band. In the blue band unwanted absorptions are contributed chiefly by the green absorber but also by the chlor and red absorbers. In the violet band unwanted absorptions are contributed by the blue absorber and also to a less extent by the green, chlor and red absorbers.

In the actual reduction to practice the following additional separation negatives were made and used to mask the primary records as follows:

Filters Plate to mask the violet record" 3+38 Kodak Sep. Neg. Type 1. to mask the blue record. l2+38 Kodak Sep. Neg. Type 1. to mask the green record 21+38 Kodak Sep. Neg. Type 1.

In addition the chlor record was masked from the red record. All masking was of approximately 50% strength, that is to say, positive masks were made having 50% of the density range of the negatives to which they were to be applied and then mask and negative were bound together in accurate register. These sandwiches were then used as the continuous-tone negatives from which screened half-tone positives were produced. These screened positives were then used to produce deep-etch lithographic printing plates in the usual manner. The same masked negatives could, of course, be used to make a set of letterpress plates by well-known photo engraving methods. a

The actual colorants shown in Fig. 6 are:

Violet absorber diaryl guanidine salt of Polar Yellow (0. I. 642) Blue absorber 50% of the P. T. M. A. precipitate of the Aoridine Yellow previously described.

% P. T. M. A. precipitate of 3-3-tetraethyldiamlnoacridine-HC]. Green absorber P. T. M. A. precipitate of Rhodamine G (0. I.

. 75 Chlor absorber.-. P.7 M. A. precipitate of Rhodamine 3B (O. 1. Red absorber 50%, diary] guanidine salt of Monosol Fast lue 2G8 (I. C. 1., London. England) (a sulphonated copper phthalocyanine). 50% diaryi guanidine salt of Brill, Milling Green B (O. I. 667).

They can be incorporated in a zein vehicle of approximately the following composition:

. Pounds l-methoxy-2-propanol 42.6 Water 28.4 Zein 10.0 Colorant and extender -20 locations of the absorption centers of the ideal absorbers for a S-primary process and also the practical ones listed above and illustrated in Figs. 5 and 6, and also the range within which other practical absorbers might center. All figures are in millimicrons:

Ideal Fig. 5 Fig. 6 Range blue 482. 5 465 480 460-485 green L 529. 5 510 524 505-530 chlor 574. O 553 656 550-575 The practical absorbers all have absorption bandwidths (within which absorption, expressed as density, is at least half the maximum) of about 100 millimicrons. The concepts of absorption centers and band-width are not applicable to the violet and red absorbers becaus they operate at the ends of the visible spectrum. They must obviously, however, have predominant absorption in the range 435 and shorter and 600 and longe respectively.

It will be apparent from the above that one aspect of the invention consists of a process ofreproducing multicolor object fields by exposing.

light-sensitive emulsion layers of photosensitive elements to said fields through five appropriate filters which produce responses peaking in the ranges described above and appropriately narrow.

The elements are thendeveloped, fixed, washed, and dried and five color separation negatives are.

(4) a purple whose light absorption centers in the range 550 to 575 millimicrons, and (5) a cyan which absorbs generally at 600 millimicrons and longer wavelengths. Images (2), (3) and (4) should preferably have absorption bands whose widths are not greater than millimicrons. The subtractive color component images, which may be in the form of various dyes, pigments, inks of organic or inorganic type, color developed dye images wherein the dyes are quinoneimine or azomethine dyes which are obtained by the color-coupling development of latent silver images with n-diethylamino-aniline in the presence of a color former, e. g., a phenol, naphthol,

pyrazolone, acylacetamide, etc., derivative, color toned images, etc., are superposed in register.

When they are superposed in register on a trans-,-

parent or opaque surface either multicolor transparencies or reflection prints are formed.

The 5-color reproduction processes of this invention have wide utility in the art of color reproduction. It is of general application in thephotographic and graphic arts including con-- tinuous-tone and half-tone dot structur processes including photogravure processes of printing multicolor pictures.

In the foregoing specification and in the accompanying claims it will be understood that the converting of images into colored images may be accomplished either photographically (by any of the methods now in common use) or mechanically (by any of the printing methods now in (2) an orange-pink or commonuse, e.. g reliefgiplanographic; onintage :5

lmprintation thereof upon :thepaper, or. after imprintation.

An advantage. of theinvention is that it provides' a process which more faithfully reproducesa: multicolor scene. 'A further-"advantage is that it is automatic and-eliminates the necessity-for printing a black-key=irnage and/ or localized color correction; H w

A still furtheradvantage residesin the fact that -'a-vvide range of color gamut'ca'n 'be-reproe ducecl with the five components thus eliminating the need fora large number of "difierentcolored' inks commonly usedin the graphic arts. As "many widely diiferentfembodiments of this invention can be made without d'epartingjfrom' th'e spirit anclscope thereofg'it is to be unclerstood that'ithe' invention is not tobe limitedflexcept as' definedbythe-clairns.

What is 'claimed'is: 1 p 1. In a five-component subtractive color' repr'o duction process; thesteps which'comprise' exposlng five light-sensitive photographic layers to pro-f ducefive color separationnegatives throughlight filters which willproducerespcnse peaks'fin the ranges 425 to '445, 610 to 6501472 to 492,525 to 545, and 564 to 584 millimicrons, respectively,'developing-the latent images so produceclgconverting the resulting negative images to five"col-* ored positive images, which have predominant abjsorptionin the ranges 435 millimicrons and'short-i er, 600 millimicrons and longer, and absorptions centeringin the. ranges 460 to 485, 505 to" 530, and 550 to 575. mi llimicrons,' respective1y,'and su= perposing said'positive colored images in register.

1 2. In. a. five-componentsubtractive color repifoe" duction process. the. steps which comprise "X-I posing five light-sensitive photographic. layers to; produce five. color. separation negatives through. light filterswhich will produce response peaksin the. respective ranges 425. to. 445, 61,0" tQ 6501i 472: to492, 525 to .545, and .56i4 toI584fmillimicron's and which have a transmission hand widthsj not greater. than GQrnillimicrons, developing, the; l'a tent: images .soproduc'ed, converting the s-ulting negative images; to V five colored. positive images which have predominantabsorption in the ranges 435. .millimicrons and, shorter, 6601. muunncre s; and longer-,AGO. to-485,; and 505 .to 5 mm; 550 fto} 57-5 ,millimicrons,respectively, and; superposing; -P i a Qmd ima e e rs 3. In a fivescomp nentsub act e 0x2 91?- cluction process; the steps which comprisewexposing. five light sensitive -photographic layers;to. produce :five I col separation; negatives through, light filters .'Wh i.Ch;:Wi11 produce responsepeaks inthezranges 425 to .445, 510402659, 4,72 and 492, and; 525; to: 452,1 and15564 tc' v 584 millimicrens; respeq!;. tively, developing the latent imQIEBS'JSO DI' DCiQQGQ P prin in five color sep ration nosit veim ee reconds therefrom,.:converting saidzirnages into col oreclzimages, which have predominant absorption: im;the.:ra-nges. 435.: mil1imicrons=.-.and; shorter; 60D; millimicronsi and-; -longer,- ;.and; ahsorptionsi center, ing imthearanges 4601M; 4.35;.and-rz505to 53.0,? 1ds 556eto .575; millimicrons,= respectively, and: super-- posing said colored imagesin register.-

4'.,:In'..1a. five-component subtractive color reproduction? process; the 'steps which comprise exposing fiveFlight-sensitive photographic layers to produce; five: color separation negatives through lightsfiltersewhich will produce response peaks in thesranges425=to 445; SID-to 650, 472 to 492, 525 to:545;:anr1, 564 :to'-584-:mi11imicrons,, respectively developing-the latent images: so produced, making...five'respe.ctive :printing: plates,- with positive images. "fro-m5 the developed-images and making separate: successive imprintations therefrom in register on sheet material from, inks: containing .7 colorantsywhich have predominant absorption in the-ranges.435-mi1limicrons and shorter, 600 millimicrons i and longer; and; absorptions" centering in ithezranges 460c'to 485, 505 to 530 and 550 to 5fl-5'millimic'rons; respectively;

5.1 In a fi-ve component subtractive color repro- 'duction -pr ocess, the steps-which comprise exposing.:five-light-sensitive photographic layers to produce five: color separation negatives through lightfilters which will produceresponsepeaks in the respective ranges-4'25 to 445, 610110-650, 4'72 to 492, 525 to 545, and 564 to 584 millimicrons, re-

spectively, and having, a transmission bandwidthnot. greaterthanfil) millimicrons at onehalf the-maximum transmission, developing the latent images so produced, making five respective printing plates with positive images from the developed images and making separate successive iiriprintations from the developed'images in registerjon'sheet material from inks containing colorants which have predominant absorption in the ranges 435mi1lirnicrons and shorter, 600'mi1- limicrons and" longer, and absorptions centeringi'ri the ranges'45O to 485, 505130 530, and 550 to 5'75 milliniicrons,"respectively.

6. In a process ofv reproducing multicolor pictures in which'five separate light-sensitive-layers are exposed to different spectral ranges of light and: are'converted' into positives in five subtractive colors which collectively absorb throughout thevisible spectrum, two of which; layers are exposed through light filters which will produce response peaks in the ranges 425 to 445 and-4'72 to 492 millimicrons',"respectively, the steps which comprise forming'superposed partial image records in colorants of such five subtractive-colors, one of' which colored image records absorbs at 435; millimicronsv and. shorter and the other. of-..

posing two of the said light-sensitive photographic'layers through'lightfilters which produce responses" peaking at 425 to-445 and 472- to 492 millimicrons; respectively; having'halfiwidths of not morethantvmillimicrons; developing the resultant two latent negative image records and converting ;.the negative 4 image recordsrespec tively, to-two colored positive images, one of WhiChabsorbs r at .4315 millimicrons; and shorter wavelengths,- and. theother oi which hasan absorption centering in the trange of 460 to 485 milliinicrons and having aybanda-width not over about lfifiijm-illimicronsp and: corresponding, respectively withgsaidresponsepcakssa.

8 In a five-component subtractive color reproduction process in which five separate, light-sensitive layers are exposed to different spectral ranges of light and the resultant images are converted into positive images in colorants which collectively absorb throughout the visible spectrum, the step which comprises exposing one light-sensitive photographic layer to produce a response of half-width not greater than 60 millimicrons and having a maximum in the range 564 to 584 millimicrons, developing the latent image formed and utilizing the image so produced to create a positive image in a purple colorant having an absorption centering in the range 550 to No references cited.

Certificate of Correction Patent No. 2,508,213 May 16, 1950 JOSEPH A. BALL It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 2, line 33, for a before specification read the column 7, line 68, for 525 to 452 read 525 to 545;

and that the said Letters Patent should be read as corrected above, so that the same may conform to the record of the case In the Patent Office.

Signed and sealed this 7th day of November, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

1. IN A FIVE-COMPONENT SUBTRACTIVE COLOR REPRODUCTION PROCESS, THE STEPS WHICH COMPRISE EXPOSING FIVE LIGHT-SENSITIVE PHOTOGRAPHIC LAYERS TO PRODUCE FIVE COLOR SEPARATION NEGATIVES THROUGH LIGHT FILTERS WHICH WILL PRODUCE RESPONSE PEAKS IN THE RANGES 425 TO 445, 610 TO 650, 472 TO 492, 525 TO 545, AND 564 TO 584 MILLIMICRONS, RESPECTIVELY, DEVELOPING THE LATENT IMAGES SO PRODUCED, CONVERTING THE RESULTING NEGATIVE IMAGES TO FIVE COLORED POSITIVE IMAGES WHICH HAVE PREDOMINANT ABSORPTION IN THE RANGES 435 MILLIMICRONS AND SHORTER, 600 MILLIMICRONS AND LONGER, AND ABSORPTIONS CENTERING IN THE RANGES 460 TO 485, 505 TO 530, AND 550 TO 575 MILLIMICRONS, RESPECTIVELY, AND SUPERPOSING SAID POSITIVE COLORED IMAGES IN REGISTER. 